This invention relates to excavation cutting tools, and more particularly to a retention system for retaining an excavation cutting tool holder in a support block during use.
Excavation cutting tool assemblies for such applications as continuous mining or road milling typically comprise a cutting tool, sometimes referred to as a cutting bit, rotatably mounted within a support block. The support block in turn is mounted onto a drum or other body, typically by welding, which in turn is driven by a suitable power means. When a number of such support blocks carrying cutting tools are mounted onto a drum, and the drum is driven, the cutting tools will engage and break up the material which is sought to be mined or removed. The general operation of such a mining machine is well known in the art.
Because the support block is exposed, it is subject to wear and abuse and must be cut or torched off the drum and replaced when unusable. In order to prolong the life of the support block, a cutting tool holder, sometimes referred to as a cutting tool sleeve, bit holder, or bit sleeve, is sometimes employed. The cutting tool is rotatably or otherwise releasably mounted within the bit holder which in turn is mounted within the support block via some mechanical connection. This helps to protect the support block from abuse and wear, thus minimizing or eliminating the down time periods otherwise required for drum repair. The use of such bit holders is well known in the art. For example, U.S. Pat. No. 5,067,775 to D'Angelo discloses the use of such a bit holder which is referred to as a sleeve in that patent.
It is well known that such cutting tools and cutting tool holders are subjected to considerable stresses during mining or other operations. Accordingly, it is desirable that the cutting tool holder be mounted to the support block in such a manner as to minimize movement of the cutting bit holder in order to maximize the life of the cutting tool. It is also important that the mounting between the cutting tool holder and the support block be resistant to vibratory loosening which could likewise lead to premature cutting tool wear and failure. Various methods have been proposed or used in the past to mount a cutting tool sleeve within a support block in an attempt to minimize cutting tool holder movement or loosening, while maximizing cutting tool life.
For example, U.S. Pat. No. 3,749,449 to Krekeler discloses a support block having two upstanding members or bifurcations which define therebetween a channel into which fits a tool holder. A pin passes through the support block and the cutting tool holder and releasably secures the tool holder to the support block. The Krekeler patent relies on cooperation between the bottom surface of the cutting tool holder and an upper surface of the support block, at the bottom of the channel, to resist forces tending to pivot the cutting tool holder about the pin. In other words, the Krekeler patent relies upon a close tolerance fit to minimize rotational movement of the cutting tool and cutting tool holder about the pin during use. Otherwise, movement of the cutting tool holder in the support block will cause unnecessary wear to the cutting tool, the cutting tool holder, and the support block.
Alternatively, U.S. Pat. No. 4,650,254 to Wechner discloses the use of two bolts to connect a cutting tool holder to a block. The two bolts pass horizontally through the rear surface of the support block and through the shank portion of the cutting tool holder. Such a connection may be subject to vibratory loosening.